1. Field of the Invention
The present invention relates to a composition superior in water resistance which comprises a specific polyvinyl alcohol resin.
2. Description of the Prior Art
Polyvinyl alcohol (occasionally referred to as PVA hereinafter) has been widely used as a variety of binders, adhesives, and surface-treating agents. It is unrivaled by any other water-soluble resins in its good film-forming properties and high strength. Unfortunately, it suffers a disadvantage of being poor in water resistance, especially water resistance at low temperatures in a dry state, because of its water solubility. Several methods have been proposed to eliminate this disadvantage. Examples include its crosslinking with glyoxal, glutaraldehyde, dialdehyde starch, water-soluble epoxidized compound, or methylol compound. A disadvantage of the crosslinking method is the necessity of heat treatment for a long time at an elevated temperature above 100.degree. C., or above 120.degree. C., render the PVA completely water resistant. On the other hand, rendering PVA water resistant at low temperatures in a dry state needs a strong acid condition at a pH 2 or below. This method poses problems with instability in the viscosity of PVA aqueous solution and with gelation during use. In addition, the resulting product does not exhibit satisfactory water resistance. Other known methods include crosslinking carboxylic acid-containing PVA with polyamide epichlorohydrin resin and crosslinking acetoacetyl group-containing PVA with glyoxal (or any other polyaldehyde). These methods still present a disadvantage in that the resulting product does not exhibit satisfactory water resistance and its aqueous solution has poor viscosity stability.